1. Field of the Invention:
This invention relates to quartz crystal oscillation circuits.
2. Discussion of the Prior Art:
Commonly available quartz crystal oscillation circuits vary the oscillation frequency by employing a variable capacity diode as a part of the load circuit of the quartz crystal resonant element and by varying the bias voltage applied to the diode. The oscillation frequency can thus be varied by changing the load capacity. However, with the conventional quartz crystal oscillation circuits, the output amplitude fluctuates and further the output amplitude falls off when the load capacity varies greatly. Therefore, it is difficult to extensively vary the oscillation frequency. From a practical point of view, a sufficiently adjustable compensation circuit is also required in order to make up for frequency deviation induced by manufacturing processes. All of these factors reduce the operationally effective range of variable frequency. Therefore, it is almost impossible for a conventional oscillator to perform the receiver incremental tuning function in transceivers.